Publications

The limited efficacy shown by drug delivery systems so far prompts the development of new molecular approaches for releasing drugs in a controlled and selective manner. Light is a privileged stimulus for delivery because it can be applied in sharp spatiotemporal patterns and is orthogonal to most biological processes. Supramolecular polymers form molecular nanostructures whose robustness, versatility, and responsivity to different stimuli have generated wide interest in materials chemistry. However, their application as drug delivery vehicles has received little attention. We built supramolecular polymers based on discotic amphiphiles that self-assemble in linear nanostructures in water. They can integrate diverse amphiphilic bioligands and release them upon illumination, acutely producing functional effects under physiological conditions. We devised two strategies for drug incorporation into the photoswitchable nanofibers. In the co-assembly strategy, discotic monomers with and without conjugated bioligands were co-assembled in helicoidal supramolecular fibers. In the drug embedding approach, we integrated a potent agonist of muscarinic receptors into the discotic polymer by noncovalent stacking interactions. This ligand can be released on demand with light ex situ and in situ, rapidly activating the target receptor and triggering intracellular responses. These novel discotic supramolecular polymers can be light-driven drug carriers for small, planar, and amphiphilic drugs.

JTD Keywords: Delivery, Doxorubicin, Glutamate-receptor, Nanoparticles, Nanostructures, Optical control, Paclitaxe

To interrogate neural circuits and crack their codes, in vivo brain activity imaging must be combined with spatiotemporally precise stimulation in three dimensions using genetic or pharmacological specificity. This challenge requires deep penetration and focusing as provided by infrared light and multiphoton excitation, and has promoted two-photon photopharmacology and optogenetics. However, three-photon brain stimulation in vivo remains to be demonstrated. We report the regulation of neuronal activity in zebrafish larvae by three-photon excitation of a photoswitchable muscarinic agonist at 50 pM, a billion-fold lower concentration than used for uncaging, and with mid-infrared light of 1560 nm, the longest reported photoswitch wavelength. Robust, physiologically relevant photoresponses allow modulating brain activity in wild-type animals with spatiotemporal and pharmacological precision. Computational calculations predict that azobenzene-based ligands have high three-photon absorption cross-section and can be used directly with pulsed infrared light. The expansion of three-photon pharmacology will deeply impact basic neurobiology and neuromodulation phototherapies.© 2023 Wiley-VCH GmbH.

JTD Keywords: absorption, azobenzene photoswitches, deep, glutamate-receptor, intravital microscopy, multiphoton excitation, muscarinic neuromodulation, photopharmacology, two-photon lithography and polymerization, 2-photon excitation, Animals, Azobenzene, Infrared rays, Ligands, Multiphoton excitation, Muscarinic neuromodulation, Photons, Photopharmacology, Photopharmacology, azobenzene, muscarinic neuromodulation, multiphoton excitation, two-photon lithography and polymerization, Two-photon lithography and polymerization, Zebrafish

Artificial control of neuronal activity enables the study of neural circuits and restoration of neural functions. Direct, rapid, and sustained photocontrol of intact neurons could overcome the limitations of established electrical stimulation such as poor selectivity. We have developed fast photoswitchable ligands of glutamate receptors (GluRs) to enable neuronal control in the auditory system. The new photoswitchable ligands induced photocurrents in untransfected neurons upon covalently tethering to endogenous GluRs and activating them reversibly with visible light pulses of a few milliseconds. As a proof of concept of these molecular prostheses, we applied them to the ultrafast synapses of auditory neurons of the cochlea that encode sound and provide auditory input to the brain. This drug-based method afforded the optical stimulation of auditory neurons of adult gerbils at hundreds of hertz without genetic manipulation that would be required for their optogenetic control. This indicates that the new photoswitchable ligands are also applicable to the spatiotemporal control of fast spiking interneurons in the brain.

JTD Keywords: Acid, Azobenzene, Glutamate-receptor, Ion channels, Mechanisms, Nerve, Optical switches, Release, Stimulation

Although the identity and interactions of signaling proteins have been studied in great detail, the complexity of signaling networks cannot be fully understood without elucidating the timing and location of activity of individual proteins. To do this, one needs a means for detecting and controlling specific signaling events. An attractive approach is to use light, both to report on and control signaling proteins in cells, because light can probe cells in real time with minimal damage. Although optical detection of signaling events has been successful for some time, the development of the means for optical control has accelerated only recently. Of particular interest is the development of chemically engineered proteins that are directly sensitive to light.

JTD Keywords: Ion channels, Acetylcholine receptor, Glutamate-receptor, Potassium channel, K+ channel, Light, Neurons, Channelrhodopsin-2, Manipulation, Activation